Spark-plug.



1. l. MACBETH.

SPARK PLUG.

APPLlcATloN FILED Aue.26. 19m.

Patented Apr. 29, 1919.

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NVEJVTOR. Waclftyx BY /f AUTOR :milonic J. HACBETH, or DAYTON, onto.

snm-PLUG.

' Specification of Letters Patent.

Application med August 26, 1913. Serial No. 251,412.

i To all what?, t may concern.'

Be it known, that I, J EREMoNT J. M Ac- BETH, a citizen, of the UnitedStates, residui at Dayton, in the county of Montgomery an State of Ohio,have invented certain new and useful Improvements in Spark-Plugs, ofwhich the following is a speclication. E

My invention comprises an improved `spark plug of the type used inconnection with gas engines. l

The object of the invention 1s to improve the method of manufacture ofspark plugs with a view to simplifying the same and reducing themanufacturing cost, and at the same time provide a durableand highlyeili-` cient spark plug. g The improvements have to do more speciallywith the mounting of the insulator bodies whereby a minimum use` is madeof screw thread connections and the work of assembling the parts is`relatively simple, and efficiency is preserved.

A knowledge of the invention w1l1 be readily gained from the followingdescription thereof in connection with theaccompanying drawing which isa longitudinal sectional elevation made upon a scale somewhat largerthan the actual size of the spark plug in order to more clearlyillustrate the elements thereof.

Referring more? specifically to these elements, 1 designates the outershell or main bod of the Plug, the upper end terminating in t e form ofa dome 1. The lower portion of said shell or main body is provided withexterior `screw threads 10 for attaching the plug to the cylinder of anengine (not shown). The body of said shell or body is provided with anenlarged portion` in the4 form of a nut 2 by which the attachment ismade with the cylinder of thel engine, this nut 2 being formed integralwith said shell. 3 desi ates an internal body of insulation, such orexample, as porcelain. The lower portion of this porcelain .body 3yisenlarged to conform to the dome shaped character of `the outer shell inwhich it is housed. The

upper portion of said insulator 3 is reduced in diameter and extendsabove and out of I the internal insulator 3. The upper end of thedome-shaped' end of the outer shell. 4

the insulatorfbody 4 is provided with a recess 16 which is larger inarea thanthe portion of the internalinsulator body 3 pro- ]ects. Withinthe space between the internal insulator 3 and the body or outer shell1` and the space between the upper portion of the internal vinsulator 3and the outer insulator portion 4 cementitious material 'Z and 5 isplaced for the purpose of tightening or `sealing the respective bodiestogether. 8

designates a terminal stem or electrode which passesy through theinternal insulator 3 and the nut 12 and holds or supports the said internal insulator?, by an, integral collar` 9 formed on said stem belowthe said insulator. The upperportion of the electrode or Patented Apr.29, 1919.

y opening of said body 4=-into which the upper4 stem 8,is provided withscrew threads 13 which are engaged by the nut 12. The nut 12, as beforestated, is received by the recess 16 in the upper end of the outerinsulator body 4 and the same is instrumental in supporting theelectrode 8 and the internal insulator 3 in position,` said nut engagingthe annular shoulder 17 which is formed atthe j bottom of the recess 16.The space between rbody 1 and pointing in proximity to the end of thestern or electrode 8 and providing in connection therewith the sparkingpoint 16".

From the description given above it will `be seenthat the internalinsulator 3 is inserted into the outer shell orbody 1 through the endhaving the larger opening and that it is held securely in positiontherein ina manner which provides for a requisite amount of co-eiciencyof eX ansion and contraction. It will also be o erved that `any taperedor contracted areas are not depended upon to contribute to holding theinternal insulator in" position. It may be stated here that while thematching surfaces between the outer shell or main body and the internalYand external insulators are shown to be of rounded or of dome-shapedform it will be apparent that these matching sur? faces might be made ofa tapered or beveled i character. It is thought, however, that therounded form is more preferable.

Havingdescribed my invention, I claim: In a spark plug,the combinationof an g e a 1 .1,301,832 i outer shell having a` rounded end, an inner`ed end of theouter shell and into whiohthe insulator body fillingvtherounded end of' reduced portion of the innerinsulator pro- 1o said shellandY having o. reduced portionof J and a nut engaging said electrodeuniform diameter extending beyond said mem r and' supporting the same onsaid '5 end, a. straight electrode member extending, puter insulatorbody.

through said inner insulator body and the In testimony whereof Iax mysignature. reduced extended portion thereof,an 'outerv I insulator bodyformed to receive the rou'nd- JEREMONT J.A MAOBETH.

